Electric fences are employed for both security purposes and for stock control in countries worldwide. Despite the proliferation of such electrified fences, the basic means of construction and operation are fundamentally the same, whereby a fence used to prevent movement through a given area is normally formed by a plurality of individual spaced apart (typically parallel) electrified wires/strands extending across the said space (either vertically or horizontally). In order to maintain the appropriate electrical connections, a common connector is attached across the individual wires to provide power to each electrified element.
Typically on longer sections this system requires each individual electrified wire to be individually tensioned, to provide both physical and electrical barrier properties, and to be securely affixed and insulated from the end post upon which all the said electrified strands are terminated. This is both time consuming and expensive and requires a certain degree of skill to ensure correct installation. Furthermore, to achieve the above mentioned tension required for each individual electrified element, typical known systems hard-wire the electrified element to an insulator at one end of the fence enclosure and use a ratchet mechanism at the other end to provide the said tension. This system requires an individual ratchet mechanism for each electrified strand/wire.
It would be clearly advantageous therefore to form an electrified fence from a reduced number of electrified strands, associated insulators, and ratchet/tensioning mechanisms.
In most security applications and some stock control fences, a separate earth or low voltage strand is employed in addition to the high voltage strand. This ensures a potential difference between an individual or stock contacting the two strands.
On fences with shorter sections formed with wires of different potential (e.g. where one wire acts as an earth, or low voltage potential wire and the other as a phase wire, or high voltage potential wire), it is known to use continuous strands of wire alternating between opposing supports of a fence. However, each strand is effectively tied off at each insulator by applying a number of turns of the wire around the insulators at either support.
As the phase and earth wires (for example) typically form alternate spans between the supports of the fence, some means is required to avoid a short-circuit as the strands cross each other at the supports of the fence. In the prior art, this is achieved by bending an earth wire outwards from the plane of the fence between two insulators on the same side of the fence, looping over the intermediate insulator carrying the other wire of different voltage potential.
The same procedure is adopted for the other wire, though with the looped section of the wire being bent outwards from the plane of the fence in the opposite direction to the first wire to avoid shorting/interference.
However, this configuration produces numerous drawbacks including:                difficulties in tensioning/re-tensioning individual spans after the fence is constructed;        the vulnerability of the projecting looping sections of wire to being snagged and/or damaged by passing vehicles/people/animals;        an aesthetically undesirable appearance; and        difficulties in concealing which wire is the low voltage/earth strand.        
It is possible for an assailant to scale an electric security fence by only holding the successive earth strands spanning the gate/fence.
Therefore, it is desirable to make it difficult for an assailant to visibly discern the live strand from the earth strand.
Known means of accomplishing this for fences utilising multiple individual strands joined by configuring wires include the use of complex fittings that clamp several live and earth strands in a manner that obscures the electrical continuity of each strand. Such fittings are however difficult to implement and service and expensive to make.
The same principles apply to fences using variants of the high voltage—earth strand combination. Such variants include applying different high voltage potentials to both strands, or offsetting the instance of the high-voltage pulses, as described in European Patent No. 0843954, U.S. Pat. No. 5,973,413, Australian Patent No. 705977 and South African Patent No. 96/6799 stemming from the applicant's patent PCT/NZ0096/00081, incorporated herein by reference.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.